A metal coping is used in dentistry in the construction of a dental crown and bridge. The metal coping functions as the understructure of the crown and is usually covered, for reasons of aesthetics, with a fired-on coating of ceramic porcelain composition or an acrylic. The metal coping supports the coating and provides the required structural strength and rigidity for the restored tooth to resist the forces of mastication.
The customary practice is to cast the metal coping from an investment of a wax or plastic pattern of the tooth to be restored. The restoration formed using this procedure is conventionally referred to as a cast metal restoration. A metal coping has recently been developed for constructing a porcelain to metal crown which does not require waxing, investing or casting. The coping is formed from a prefabricated metal foil arranged in a prefolded configuration, with a plurality of foldable sections, as described in more detail, in U.S. Pat. No. RE. 33,099, which issued to Applicant on Oct. 24, 1989. An alternative method of forming a dental coping from a metal foil is taught by Applicant in U.S. Pat. No. 4,861,267, which issued on Aug. 29, 1989. In each instance, the starting material for forming the coping is a solid metal foil formed from a lamination of solid metal layers, each of a precious metal.
As an alternative to the use of a prefabricated metal foil, Applicant developed a dental material composition, as disclosed in U.S. Pat. No. 4,997,694, which is capable of being molded into a desired shape, which is self-supporting in the molded configuration, and which will retain the shape in which it is molded under heat treatment. The dental material, as taught in the aforementioned patent, the disclosure of which is herein incorporated by reference, comprises a metal composition, including particles of high-fusing temperature metal having a melting temperature above a preselected heat-treatment temperature, and metal particles of a low-fusing temperature, which substantially melts during heat treatment at such heat-treatment temperature to form a porous, sponge-like structure, with the high-fusing temperature metal particles interconnected by the melted, low-fusing temperature metal. Applicant further teaches in U.S. Pat. No. 4,990,394, that the porous, sponge-like structure should provide a total void volume of between twenty (20%) to eighty percent (80%).